Clothes washing machines typically include a drain pump for pumping water from the washing container, or tub, prior to beginning a spin cycle. The pump typically is located below the tub so that water drains, due to gravity forces, from the tub and into the pump. Draining the free water, i.e., water not absorbed in clothes located in the tub, from the tub prior to the spin cycle improves washing machine performance during the spin cycle by decreasing the occurrences and severity of out of balance loads.
Although draining the water from the tub before the spin cycle provides performance advantages, if the pump continues pumping operations after the tub is substantially empty of free water and before the spin cycle, a pump gurgling noise will be generated as the pump oscillates between pumping water and air. Once the basket begins to spin, water extracted from the clothes flows from the tub to the pump inlet and the pump gurgling noise temporarily stops. However, as the spin cycle proceeds, the amount of water extracted from the clothes will decrease and the pump will resume surging due to a lack of water at the pump inlet.
The pump gurgling noise may be annoying, particularly to occupants of a residence if the washing machine is located in a living area of the residence. It would be desirable to contain such gurgling noise within the washing machine, without adversely affecting the performance of the machine.
Known attempts to contain the gurgling noise include positioning a flapper valve over the tub water outlet. The flapper valve is biased so that water can flow from the tub to the pump but blocks flow from the pump toward the tub. In operation, once all the free water has been drained from the tub, the flapper valve closes and blocks the pump gurgling noise from the tub. Similarly, during the spin cycle, once the water has been extracted from the clothes in the tub, the flapper valve closes and again blocks the gurgling noise. By blocking the pump gurgling noise from the tub, the gurgling noise is substantially contained in the washing machine.
Although the flapper valve does facilitate containing the gurgling noise, the flapper valve is expensive to design and manufacture. Moreover, it is believed that with a flapper valve, lint can accumulate at the valve, thereby decreasing the pump out rate of water from the tub and trapping suds in the basket.
Another known device includes electrical sensors located in the tub so that once the water level within the tub falls below some predetermined level, the pump motor is deenergized. If the pump motor is deenergized before the water level falls to a level at which the pump begins to generate the gurgling noise, the gurgling noise can be eliminated. Such electrical sensors and controls, however, also add cost and complexity to the washing machine.
As explained above, it would be desirable to contain the pump gurgling within the washing machine. In addition, it would be desirable to provide such noise containment without substantially increasing the cost and complexity of the washing machine.